1. Field of the Invention
The present invention relates to the SCSI (Small Computer Systems Interface) and Ethernet adapter boards used in personal computers which interface with the PCI (Peripheral Component Interconnect) Local Bus. More particularly, the present invention relates to replacement of the SCSI and Ethernet adapter boards with a single chip.
2. Description of the Prior Art
The PCI Local Bus is a high performance, 32-bit or 64-bit bus with multiplexed address and data lines. As illustrated in FIG. 1, the PCI Local Bus 100 is intended for use as an interconnect mechanism between peripheral controller components, such as the SCSI adapter board 102, Ethernet adapter board 104, and processor/memory system 106. A PCI Local Bus Specification, Rev. 2.0, effective Apr. 30, 1993 includes protocol, electrical, mechanical and configuration requirements for the PCI Local Bus components and expansion boards. Further information concerning the PCI Local Bus specification can be obtained from the PCI Special Interest Group, M/S HF3-15A, 5200 NE Elam Young Parkway, Hillsboro, Oreg. 97124-6497.
Ethernet is a standard in personal computer networking. An Ethernet adapter board provides components for transmitting and receiving signals on a network allowing a personal computer in which it resides to be networked with other personal computers. A PCI bus interface unit on the Ethernet adapter board interfaces the adapter board with the PCI Local Bus on which a CPU resides. The PCI bus interface unit may provide digital signals to control the PCI Local Bus.
SCSI is a standard that allows users to easily add up to seven peripheral devices on a personal computer such as CD-ROM and high capacity disk drives. A SCSI adapter board in a personal computer provides digital address, data, and control signals to a SCSI bus on which peripheral devices reside. A PCI bus interface unit on the SCSI adapter board interfaces the adapter board with the PCI Local Bus on which a CPU resides. The PCI bus interface unit may provide digital signals to control the PCI bus.
Previously, manufacturers have provided Ethernet and SCSI components spaced apart on separate adapter boards. The high current requirements for digital signals transmitted and received on the PCI and SCSI buses means that the digital signals can generate significant noise. With sensitive analog components in the Ethernet controller, such as the phase lock loop (PLL) circuitry, such noise has prohibited integration of components of the Ethernet and SCSI adapter boards.